.eslintrc.js

// These are allowed to require packages from devDependecies
const devScripts = ['**/next.config.js', '**/stepDefinitions.*'];

module.exports = {
  root: true,
  env: {
    browser: true,
    commonjs: true,
    es6: true,
    node: true,
  },
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaVersion: 2018,
    sourceType: 'module',
    ecmaFeatures: {
      jsx: true,
    },
  },
  plugins: ['react-hooks', '@typescript-eslint', 'chai-friendly'],
  extends: [
    'airbnb',
    'prettier',
    'prettier/react',
    'prettier/@typescript-eslint',
    'plugin:import/recommended',
    'plugin:import/typescript', // Allow js file import ts files.
  ],
  settings: {
    react: {
      version: 'detect',
    },
    // https://www.npmjs.com/package/eslint-import-resolver-typescript
    'import/resolver': {
      // use <root>/tsconfig.json
      typescript: {},
    },
  },
  rules: {
    // urm... the whole immer is based on param-reassign.
    'no-param-reassign': 'off',
    // airbnb errors on for..of and for...in but we want these.
    'no-restricted-syntax': ['warn', 'WithStatement', 'LabeledStatement'],

    'react/jsx-filename-extension': ['error', { extensions: ['.tsx', '.jsx'] }],
    'react/jsx-props-no-spreading': 'off',
    'react/prop-types': 'off',

    // So props are not seen as unused vars (rule from https://github.com/vercel/next.js/blob/canary/.eslintrc.json)
    'no-unused-vars': 'off',
    '@typescript-eslint/no-unused-vars': [
      'warn',
      {
        args: 'none',
        ignoreRestSiblings: true,
      },
    ],

    // Allow dev scripts (like next.config.js) to import from dev dependencies.
    'import/no-extraneous-dependencies': [
      'error',
      // scripts that are allowed to import from devDependencies
      // Because all devDependencies are in root, we need an .eslintrc per package
      // that points the packageDir for this rule to the root.
      // See .eslintrc on each package
      { devDependencies: devScripts },
    ],
    // https://github.com/benmosher/eslint-plugin-import/issues/1615#issuecomment-577500405
    'import/extensions': [
      'error',
      'ignorePackages',
      {
        js: 'never',
        jsx: 'never',
        ts: 'never',
        tsx: 'never',
      },
    ],
  },
  overrides: [
    // Tests
    {
      files: ['**/stepDefinitions.*'],
      rules: {
        'func-names': 'off',
        'prefer-arrow-callback': 'off',
        'no-unused-expressions': 'off', // So it doesn't complain with "expect(loginFn).to.be.called"
        'chai-friendly/no-unused-expressions': 'error', // So it doesn't complain with "expect(loginFn).to.be.called"
      },
    },
  ],
};